Develop Reference

Motion in Crafty.js

Im trying to use the Motion component in crafty.js but I fail at the most basic things. It seems like the 'Motion' component is not added.
Like this very simple code from example code in the docs.
var ent = Crafty.e("2D, Motion");
var vel = ent.velocity(); //returns the velocity vector
vel.x; // retrieve the velocity in the x direction
vel.x = 0; // set the velocity in the x direction
vel.x += 4 // add to the velocity in the x direction
result: TypeError: ent.velocity is not a function
I can access functions in other components like Multivay, Text just fine.

Zoom my drawing on the background [duplicate]

This question already has an answer here:
HTML5 canvas zoom where mouse coordinates
(1 answer)
Closed 8 years ago.
I make program like a paint with HTML5 canvas and javascript. Drawing takes place on the background image. How to zoom my drawing on the background together.
Before zoom it:
After zoom it (need this result):
Note: zoom should be where clicked with the mouse on the background image

I've done this before!
First of all, I set a zoom level attribute on my canvas.
Main.canvas.zoomX = 1;
Main.canvas.zoomY = 1;
I also retain the original size of the canvas for reference.
Main.canvas.originW = Main.canvas.width;
Main.canvas.originH = Main.canvas.height;
I also retain the original left and top of the canvas for reference.
Main.canvas.gLeftStart = 0;
Main.canvas.gTopStart = 0;
I then set a zoom percentage. The zoom level will be adjusted by this amount every time that the zoom event occurs.
Main.canvas.zoomPerc = 0.05;
Next, I set an event listener on my canvas to watch for mousewheel.
Main.canvas.addEventListener('wheel', zoom, true);
Now, I'm going to write a quick function to retrieve the zoom, then I'll explain it.
function zoom(evt)
{
var x;
var y;
Main.canvas.xLayerS = (evt.layerX + (Main.canvas.gLeftStart * -1)) / (Main.canvas.originW * Main.canvas.zoomX);
Main.canvas.yLayerS = (evt.layerY + (Main.canvas.gTopStart * -1)) / (Main.canvas.originH * Main.canvas.zoomY);
Main.canvas.leftPerc = Main.canvas.gLeftStart / (Main.canvas.originW * Main.canvas.zoomX);
Main.canvas.topPerc = Main.canvas.gTopStart / (Main.canvas.originH * Main.canvas.zoomY);
if(evt.deltaY > 1)
{
Main.canvas.zoomX *= 1 + Main.canvas.zoomPerc;
Main.canvas.zoomY *= 1 + Main.canvas.zoomPerc;
}
else
{
Main.canvas.zoomX *= 1 - Main.canvas.zoomPerc;
Main.canvas.zoomY *= 1 - Main.canvas.zoomPerc;
}
var iiDS;
var cmd;
Main.canvas.xLayer = Main.canvas.xLayerS * (Main.canvas.originW * Main.canvas.zoomX);
Main.canvas.yLayer = Main.canvas.yLayerS * (Main.canvas.originH * Main.canvas.zoomY);
Main.context.clearRect(0, 0, Main.canvas.width, Main.canvas.height);
Main.context.beginPath();
Main.canvas.gLeftStart = (evt.layerX - Main.canvas.xLayer);
Main.canvas.gTopStart = (evt.layerY - Main.canvas.yLayer);
for(iiDS = 0; iiDS < Main.dataPoints.length; iiDS++)
{
if(iiDS === 0)
{
cmd = 'moveTo';
}
else
{
cmd = 'lineTo';
}
Main.dataPoints[iiDS].xPerc = Main.dataPoints[iiDS].x / Main.range.x;
Main.dataPoints[iiDS].yPerc = Main.dataPoints[iiDS].y / Main.range.y;
x = Main.canvas.gLeftStart + (Main.dataPoints[iiDS].xPerc * (Main.canvas.originW * Main.canvas.zoomX));
y = Main.canvas.gTopStart + (Main.dataPoints[iiDS].yPerc * (Main.canvas.originH * Main.canvas.zoomY));
Main.context[cmd](x, y);
}
Main.context.stroke();
}
Now that your canvas has been re-sized, you will need to redraw whatever was in it. Remember, any time that you re-size a canvas, you clear the canvas. If your canvas was holding an image, then that's simple, redraw that image at that size. If you canvas was holding data points (like a chart) then I would suggest that you make your data points have percentage like (probably a word for that) positions along your chart, not pixel positions.
More importantly though, I do not suggest that you ever re-size and re-position your canvas on zoom. Your page can get jumbled up and sloppy that way. Instead, use the percentages for size (like I showed you) and use the values for left and top positioning as starting points in your drawing. If a data point was a certain percentage of a way across a chart, it can be drawn at any size. Plus, you can draw outside of your canvas, it just won't be visible. Your canvas would then be more like a view-port.
You can do some really impressive charting this way, which a lot of companies pay a lot of money for. Have fun!

Did you try Context2d.scale(x, y)? You could do the following
var canvas = document.getElementById('myCanvas');
var context = canvas.getContext('2d');
context.scale(2, 2);
paintBackGround(context);
paintForeGround(context);
scale(factorWidth, factorHeight) Scales all coordinates in the canvas by the factors, so it will scale the background and the drawing. The example would double the size. You don't have to scale your coordinates by yourself, just let canvas do that for you.
Here is an example :
http://www.html5canvastutorials.com/advanced/html5-canvas-transform-scale-tutorial/
The only problem here: you need to scale before you draw, so you need a model that contains the original drawing in original unscaled coordinates, that can be drawn after scaling (paintForeGround() in my example)
Scale() is part of so called Transformations. You can Translate (move along a vector) rotate and scale the content of a canvas by using buildin functions of canvas. Just take a look at the html5canvastutorials. This works with matrix-mutliplications in the background, but it is really simple to use.

Constrain to x value using High Charts addPoint()

I was reading a bit about the high charts addPoint() function here:
http://api.highcharts.com/highcharts#Series.addPoint()
I'm quite taken the idea of creating a chart like this one:
http://www.highcharts.com/demo/dynamic-click-to-add
...but where I have a fixed x and y scale, and where the user can only place a point on the scale in multiple of 5.. such as a point at x=10 and y=20...
Has this been attempted, and/or is it feasible given the options provided in the API?
Thanks

You can modify this behavior in your click handler - you get the exact click values there, and you can simply round it to the next interval you like:
events: {
click: function(e) {
// find the clicked values and the series
var x = e.xAxis[0].value,
y = e.yAxis[0].value,
series = this.series[0];
// round given click point to intervals
x = Math.ceil(x / 5) * 5;
y = Math.ceil(y / 5) * 5;
// Add it
series.addPoint([x, y]);
}
}
The Demo of this example will give you a starting point.

Raphael JS nested transformations

I have several nested sets in Raphael JS that I want to use like layers in photoshop. That is: objects in sets may have their own transformations, and being places to a set they become relatively positioned in it. And set may have it's own transformation too.
Now it seems when a set transformation is applied, it just performs it to each element separately and with absolute position relatively the page.
With that mechanics I run into such simple problem: I have the set and the rectangle in it. Then I resize rectangle with scale(0.5,0.5,0,0); And then I want to drag the entire set. I perform dragging with set.translate(x,y). As the result I get rectangle that moves twice slower than other non-scaled items.
var rdr = this;
this.paper = Raphael(0,0,1000,1000);
this.set = this.paper.set();
this.set.push(this.paper.rect(0,0,100,100)); // non-scaled rectangle
this.set.push(this.paper.rect(0,0,100,100).scale(0.5,0.5,0,0)); // scaled rectangle
$("body").bind("mousedown.RDR",function(e) {
var ox = e.pageX;
var oy = e.pageY;
$("body").bind("mousemove.RDR",function(e) {
rdr.set.translate(e.pageX-ox,e.pageY-oy);
ox = e.pageX;
oy = e.pageY;
}).bind("mouseup.RDR",function() {
$("body").unbind("mouseup.RDR").unbind("mousemove.RDR");
});
});
How should I correct this code to make my rectangles move with the same speed?
Theoretically all that I need to move a set of objects simultaneously is a way to control the order of transformations. I haven't found built in solution so there's a little hack that inserts translation of a set "BEFORE" transformations that're already applied to elements:
Raphael.el.translateBefore = function(x,y) {
var matrix = this.matrix;
var transform = matrix.toTransformString();
transform = ("t"+x.toString()+","+y.toString()) + "," + transform;
this.transform(transform);
return this;
}
this.paper = Raphael(this.containerId,this.paperWidth,this.paperHeight);
// добавляем метод для raphael.set через жопу, не нашел нормальный способ
this.paper.set().__proto__.translateBefore = function(x,y) {
_.each(this,function(el) {
el.translateBefore(x,y);
});
return this;
}

http://raphaeljs.com/reference.html#Element.transform
// if you want you can append or prepend transformations
el.transform("...t50,50");
el.transform("s2...");

HTML canvas double buffering frame-rate issues

I have a full-screen canvas with 3 images drawn on it. When I resize the window, these images change position; however, it appears to be very glitchy, more so in Firefox.
I've been reading that double-buffering should resolve this issue, but I'm wondering how I would double buffer when the next position is unknown. That is to say, I cannot determine what should be buffered in the future, so how would this be possible?
Here is one source that seems doable, but I do not fully understand the concept Fedor is trying to explain.
Does HTML5/Canvas Support Double Buffering?
So far I have,
$canvas = $('#myclouds')[0];
$canvas_buffer = $('canvas')[0].insertAfter($canvas).css('visibility', 'hidden');
context = $canvas.getContext('2d');
context_buffer = $canvas_buffer.getContext('2d');
clouds_arr = [$canvas, $canvas_buffer];
$(window).resize(function () {
drawCanvas();
};
function initCanvas() {
// Sources for cloud images
var cloud1 = '/js/application/home/images/cloud1.png',
cloud2 = '/js/application/home/images/cloud2.png',
cloud3 = '/js/application/home/images/cloud3.png';
// add clouds to be drawn
// parameters are as follows:
// image source, x, y, ratio, adjustment)
addCloud(cloud1, null, 125, .03);
addCloud(cloud2, null, 75, .15);
addCloud(cloud3, null, 50, .55);
addCloud(cloud1, null, 125, .97, 300);
addCloud(cloud2, null, 70, .85, 300);
addCloud(cloud3, null, 45, .5, 300);
// Draw the canvas
drawCanvas();
}
function drawCanvas() {
// Reset
$canvas.attr('height', $window.height()).attr('width', $window.width());
// draw the clouds
var l = clouds.length;
for (var i = 0; i < l; i++) {
clouds[i].x = ($window.width() * clouds[i].ratio) - clouds[i].offset;
drawimage(context, clouds[i]);
}
}
function Cloud() {
this.x = 0;
this.y = 0;
}
function addCloud(path, x, y, ratio, offset) {
var c = new Cloud;
c.x = x;
c.y = y;
c.path = path;
c.ratio = ratio || 0;
c.offset = offset || 0;
clouds.push(c);
}
function drawimage(ctx, image) {
var clouds_obj = new Image();
clouds_obj.src = image.path;
clouds_obj.onload = function() {
ctx.drawImage(clouds_obj, image.x, image.y);
};
}

I think maybe you are misunderstanding what double buffering is. Its a technique for smooth real-time rendering of graphics on a display.
The concept is you have two buffers. Only one is visible at any one time. When you go to draw the elements that make up a frame you draw them to the invisible buffer. In you case the clouds. Then you flip the buffers making the hidden one visible and the visible one hidden. Then on the next frame you draw to the now newly hidden buffer. Then at the end of drawing you flip back.
What this does is stop the user seeing partial rendering of elements before a frame is complete. On gaming systems this would also be synced up with the vertical refresh of the display to be really smooth and stop artefacts such as tearing to occur.
Looking at you code above you seem to have created the two canvas elements, but you're only using the first Context object. I assume this is incomplete as no flipping is taking place.
Its also worth noting that the window resize event can fire continuously when dragging which can cause frantic rendering. I usually create a timer on the resize event to actually re-render. This way the re-render only happens once the user stops resizing for a few milliseconds.
Also, your draw routine is creating new Image objects every time which you don't need to do. You can use one image object and render to the canvas multiple times. This will speed up your render considerably.
Hope this helps.